NASA's TRMM satellite passed over Tropical Cyclone Ian three days in a row and captured rainfall and thunderstorm cloud height data about the deadly storm as it strengthened and weakened.

Tropical Cyclone Ian meandered in an area of the Pacific Ocean between Fiji and Tonga as it intensified from a tropical storm with winds of 35 knots/41 mph on January 5, 2014 to a deadly tropical cyclone with winds of 125 knots/144 mph on January 11, 2014. Tropical cyclone Ian caused extensive damage and an unknown number of deaths when it passed through Tonga at the peak of its intensity.

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The Tropical Rainfall Measuring Mission or TRMM satellite provided excellent coverage of Ian with multiple passes directly above the tropical cyclone. Rainfall data collected by TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) instruments with four passes. The first overpass on January 10, 2014 at 01:17 UTC showed Ian located between Fiji and Tonga when maximum sustained winds were estimated at 90 knots/104 mph. The second time TRMM passed over Ian was later in the day at 08:33 UTC/3:33 a.m. EST. Data from that overpass showed that Ian was much larger and better organized with a very well defined eye.

The next day, January 11, TRMM captured data on Ian when the tropical cyclone was passing close to the east of Tonga at 08:33 UTC/3:33 a.m. EST. Ian was then at its most dangerous category four intensity. TRMM data showed rain falling at the rate of over 169 mm/6.7 inches per hour around the nearly circular eye.

On January 12 at 01:05 UTC, TRMM showed a small area of heavy rainfall near Ian's center, with moderate to light rain throughout the rest of the system. By that time, Ian had moved to the southeast of Tonga.

Tropical Cyclone Ian has been battered by wind shear and infrared imagery from NASA's Aqua satellite revealed that the bulk of the precipitation has been pushed east and southeast of the storm's center.

On January 13 at 0900 UTC/4 a.m. EST, Tropical Cyclone Ian's maximum sustained winds were near 65 knots/74.8 mph/120.4 kph, just at hurricane-strength. Just a day before, Ian's maximum sustained winds were near 80 knots/148.2 kph/92.0 mph. Ian is moving to the southeast at 14 knots/25.9 kph/16.1 mph and is expected to continue in that direction. Ian was located about 882 nautical miles/1,633 km/1,015 miles south of Pago Pago, near 29.5 south and 169.9 west.

Ian has become significantly elongated as it has been battling strong wind shear. The precipitation has also been sheared to the east.

When NASA's Aqua satellite passed over Ian on January 13 at 01:23 UTC/January 12 at 8:23 p.m. EST, the Atmospheric Infrared Sounder or AIRS instrument captured an infrared picture of the storm. Infrared data showed the temperature of the storm's clouds and the sea surface temperatures surrounding it. The strongest storms with the coldest cloud tops had temperatures as cold as -63F/-52C and the AIRS image showed those storms were clearly pushed east and southeast of the center. The AIRS data also showed warmer, lower cloud top temperatures north and west of Ian's center.

AIRS data showed sea surface temperatures north of Ian were as warm as 300K/26.5C/80.3F/ while those south of Ian (and in the general direction the storm was heading) were near 290K/16.8C/62.3F or cooler.

Over the next couple of days, Ian is expected to become extra-tropical and a cold core low pressure area in the next day and a half.

Tropical Cyclone Ian is lashing the Tonga Islands in the Southern Pacific Ocean, and has prompted hurricane warnings. NOAA's GOES-West satellite captured an infrared image that showed a clear-eyed Ian over the islands.

The Tonga Islands are under warnings from Cyclone Ian. Today, January 10, a hurricane warning is in effect for the Va'Vau and Ha'apai groups of islands in the Tonga Islands. In addition, a gale warning is in effect for the Tongatapu group

NOAA's GOES-West satellite captured an infrared view of Cyclone Ian lashing the Tonga Islands on January 10, 2014 at 1200 UTC/7 a.m. EST. Ian's eye is clearly visible in the GOES image, but the Tonga Islands are under Ian's clouds. Ian's eye has cleared and slightly expanded since yesterday. Satellite imagery from NASA's Aqua satellite showed a cloud-covered eye on January 9, while today's GOES-West image shows a cloud-free eye. GOES satellites are managed by the National Oceanic and Atmospheric Administration. NASA's GOES Project at the NASA Goddard Space Flight Center in Greenbelt, Md. uses GOES satellite data to create images and animations.

Ian is a compact hurricane. At 0900 UTC/4 a.m. EST, Ian's maximum sustained winds were near 90 knots/103.6 mph/166.7 kph. Those hurricane-force winds extended 20 nautical miles/23.0 miles/37.0 km from the center. Tropical-storm-force winds extended up to 80 miles/92.0 miles/148.2 km from the center. Ian is expected to strengthen a little more through today and tomorrow before weakening.

Ian was centered about 371 nautical miles/426.9 miles/687.1 km east of Suva, Fiji, near 18.0 south and 175.1 west. Ian is moving to the southeast at 6 knots/6.9 mph/11.1 kph and is expected to continue in that direction.

Ian is generating very rough seas in the Tonga Island group. The Joint Typhoon Warning Center or JTWC noted that wave heights are as high as 23 feet/7.0 meters.

JTWC forecasters expect Ian to become extra-tropical in a couple of days as it continues to move in a southeasterly direction.

Compact Tropical Cyclone Ian has intensified to a hurricane-strength storm near the Tonga Islands and NASA's Aqua satellite captured an image of a cloud-filled eye when it passed overhead on January 9.

Tropical Cyclone Ian has been intensifying over the last several days near the Tonga Islands, in the South Pacific Ocean. By January 9 at 01:55 UTC it had reached hurricane-force when NASA's Aqua satellite flew overhead. At that time, the Moderate Resolution Imaging Spectroradiometer instrument took a visible picture of the storm that showed a cloud-capped eye and bands of thunderstorms wrapping into the center from the eastern and western sides of the storm.

There are warnings in effect for the Tonga Islands. A storm warning is in effect for the Va'vau group of islands, and a gale warning is in effect for the Ha'apai group of islands.

By 0900 UTC/4 a.m. EST on January 9, Tropical Cyclone Ian's maximum sustained winds had increased to 85 knots/97.8 mph/157.4 kph. Tropical-storm force winds extended as far as 80 nautical miles.92.6 miles/148.2 km from the center, while hurricane-force-winds extended 20 nautical miles/23.0 miles/37.0 km from the center. Ian was centered near 16.8 south latitude and 176.5 west longitude, about 287 nautical miles/330.3 miles/531.5 km east-northeast of Suva, Fija, where the storm is also known as "Tropical Cyclone 07P." Ian was crawling to the east-southeast at 2 knots/2.3 mph/3.7 kph.

The Joint Typhoon Warning Center forecast calls for Ian to intensify up to 95 knots/109.3 mph/175.9 kph before it starts to change into an extra-tropical storm in four days.

NASA's Aqua satellite passed over Tropical Cyclone Ian on Jan. 8 at 0105 UTC and the Atmospheric Infrared Sounder or AIRS instrument captured an infrared image of the storm. The strongest thunderstorms were concentrated around Ian's center and in bands north and south of the center where cloud top temperatures exceeded -63F/-52C. Those thunderstorm cloud tops have cooled over the previous 24 hours, indicating that they're higher in the atmosphere and that Ian is strengthening. The Joint Typhoon Warning Center forecast calls for Ian to reach hurricane-strength in the next day.

A tropical cyclone alert has been posted for the Va'vau group and Niuas in Tonga for January 8 as Ian continues to meander around them.

At 0900 UTC/4 a.m. EST, Tropical Cyclone Ian's maximum sustained winds were near 55 knots/63.2 mph/101.9 kph. It was centered about 275 nautical miles/316.5 miles/509.3 km east-northeast of Suva, Fiji, near 16.8 south latitude and 177.0 west longitude. Ian was moving to the north at 2 knots/2.3 mph/3.7 kph, but is expected to turn southeast in a couple of days while strengthening.

Without anything to steer Tropical Cyclone Ian, it has been meandering around the Southern Pacific Ocean. NASA's TRMM satellite captured images of the storm's rainfall and thunderstorm cloud height as it continued to maintain tropical-storm strength.

NASA and the Japan Aerospace Exploration Agency's Tropical Rainfall Measuring Mission satellite known as TRMM satellite passed above Tropical Cyclone Ian on January 6 at 1133 UTC/6:33 a.m. EST. Ian is a small tropical cyclone but TRMM's Precipitation Radar instrument found that Ian was dropping rain at a rate of over 113 mm/~4.4 inches per hour in some areas.

TRMM's Precipitation Radar data was used to create a 3-D vertical profile of Ian. The 3-D image showed some violent storms within Ian were reaching unusually high altitudes greater than 18.5km/~11.5 miles.

On January 7 at 0900 UTC/4 a.m. EST, Ian had maximum sustained winds near 35 knots/40 mph/62 kph. Ian was centered near 17.7 south and 176.1 west, about 314 nautical miles/361.3 miles/581.5 km east of Suva, Fiji. It has moved to the north at 5 knots/5.7 mph/9.2 kph.

According to the forecasters at the Joint Typhoon Warning Center, Ian is going to finally get a direction. Ian is sitting between two elongated areas of high pressure: a near-equatorial ridge to the north and a sub-tropical ridge to the south.

Computer model guidance indicates a mid-latitude trough (elongated area of low pressure) currently located over Southeastern Australia will track over New Zealand and cause a sub-tropical ridge to move eastward. The combination of those two high pressure areas are expected to create an improved steering environment after several days, taking Ian to the southeast.

Cyclone Ian formed quickly and was affecting the Tonga Islands in the Southern Pacific Ocean on January 6, 2014 as NASA's Aqua satellite passed overhead and captured an image of the storm.

The Moderate Resolution Imaging Spectroradiometer or MODIS instrument took a picture of Ian at 01:25 UTC on Jan. 6/8:25 p.m. EST on Jan. 5. The MODIS image showed a tightly wrapped low-level circulation center the strongest thunderstorms flaring up along the northern quadrant of the storm. NASA's TRMM or Tropical Rainfall Measuring Mission satellite also showed that the strongest thunderstorms were pushed north of the center of circulation.

Tonga warnings are already in force. On January 6 there was a gale warning in effect for the Ha'apai and Va'vau island group, and a tropical cyclone alert in effect for the rest of Tonga.

On January 6 at 1500 UTC/10 a.m. EST, Ian's maximum sustained winds were near 35 knots/40 mph/62 kph. Tropical Cyclone Ian is centered near 19.0 south latitude and 175.6 west longitude, about 351 nautical miles east of Suva, Fiji. Ian has no large weather system to guide it and has tracked westward at 1 knot/1 mph/1 kph.

Forecasters at the Joint Typhoon Warning Center expect Ian to make half a circle heading from a southwesterly to a southeasterly direction over the next day.

These 4 TRMM satellite images from Jan. 10-12 show the strengthening and weakening of Cyclone Ian. Red indicates heavy rainfall.

Image Credit:

SSAI/NASA, Hal Pierce

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TRMM's Precipitation Radar data was used to create this 3-D flyby animation Ian's well defined eye on January 11, 2014 at 0833 UTC/3:33 a.m. EST. Powerful thunderstorms in Ian's eye wall were found reaching heights of about 15 km/9.3 miles.

Image Credit:

SSAI/NASA, Hal Pierce

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This visible image of Tropical Cyclone Ian was taken by the MODIS instrument aboard NASA's Aqua satellite on January 6, 2014 at 01:25 UTC when Ian was moving over the Tonga Islands, Pacific Ocean.

Image Credit:

NASA Goddard MODIS Rapid Response Team

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NASA's TRMM satellite passed above Tropical Cyclone Ian on January 6 at 1133 UTC and found that Ian was dropping rain at a rate of over 113 mm/~4.4 inches per hour (red) in some areas.

NASA's Aqua satellite passed over Tropical Cyclone Ian on Jan. 8 at 0105 UTC and captured this infrared image. The strongest thunderstorms were concentrated around Ian's center and in bands north and south of the center where cloud top temperatures exceeded -63F/-52C (purple).

Image Credit:

NASA JPL/Ed Olsen

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NASA's Terra satellite captured this visible image of Tropical Cyclone Ian over the Tonga Islands in the Southern Pacific Ocean at 22:25 UTC on January 7, 2014.

Image Credit:

NASA Goddard MODIS Rapid Response Team

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NASA's Aqua satellite captured this visible image of strengthening Tropical Cyclone Ian over the Tonga Islands, in the South Pacific Ocean on January 9 at 01:55 UTC.